The present invention relates to filing cabinets, and more particularly to mechanisms adapted to prevent one or more of the drawers in the filing cabinet from being opened.
It has been known in the past to include interlock mechanisms on filing cabinets that prevent more than one drawer in the cabinet from being opened at a single time. These interlock mechanisms are generally provided as safety features that are intended to prevent the filing cabinet from accidentally falling over, a condition that may be more likely to occur when more than one drawer in the cabinet is open. By being able to open only a single drawer at a given time, the ability to change the weight distribution of the cabinet and its contents is reduced, thereby diminishing the likelihood that the cabinet will fall over.
In addition to such interlocks, past filing cabinets have also included locks that prevent any drawers from being opened when the lock is moved to a locking position. These locks are provided to address security issues, rather than safety issues. These locks override the interlocking system so that if the lock is activated, no drawers may be opened at all. If the lock is not activated, the interlock system functions to prevent more than one drawer from being opened at the same time. Oftentimes the system that locks all of the drawers and the interlock system that locks all but one of the drawers are at least partially combined. The combination of the locking system with the interlocking system can provide cost reductions by utilizing common parts.
Past locking and interlocking mechanisms, however, have suffered from a number of disadvantages. One disadvantage is the difficulty of changing the drawer configurations within a cabinet. Many filing cabinets are designed to allow different numbers of drawers to be housed within the cabinet. For example, in the cabinet depicted in FIG. 1, there are three drawers in the cabinet. For some cabinets, it would be possible to replace these three drawers with another number of drawers having the same total height as the three original drawers. This reconfirmation of the drawers is accomplished by removing the drawer slides on each side of the drawer and either repositioning the drawer slides at the newly desired heights, or installing new drawer slides at the new heights. Many drawer slides include bayonet features that allow the drawer slides to be easily removed and repositioned within the cabinet.
In the past, such reconfiguring of the drawers in a cabinet has been a difficult task because the interlocking and/or locking system for the drawers could not easily be adjusted to match the newly configured filing cabinet. For example, U.S. Pat. No. 6,238,024 issued to Sawatzky discloses an interlock system that utilizes a series of rigid rods that are vertically positioned between each drawer in the cabinet. The height of these rods must be chosen to match the vertical spacing between each of the drawers in the system. If the cabinet is to be reconfigured, then new rods will have to be installed that match the height of the new drawers being installed in the cabinet. Not only does this add additional cost to the process of reconfiguring the cabinet, it complicates the reconfiguring process by requiring new parts of precise dimensions to be ordered. Finding these precisely dimensioned parts may involve extensive searching and/or measuring, especially where the manufacturer of the rods is not the same entity that produced the new drawers being installed, or the manufacturer of the rods has ceased producing the parts, or has gone out of business.
Another difficulty with systems like that disclosed in the Sawatzky patent is the precise manufacturing that may be required to create these rigid rods. These interlock systems only work if the rods have heights that fall within a certain tolerance range. This tolerance range, however, decreases as more interlocks are installed in a given cabinet. In other words, the tolerance of the heights of these rods is additive. In order to function properly, a cabinet with ten drawers will therefore require smaller tolerances in the rods than a two drawer cabinet. In order to create rods that can be universally used on different cabinets, it is therefore necessary to manufacture the rods within the tight tolerances required by the cabinet having the greatest expected number of drawers. These tight tolerances tend to increase the cost of the manufacturing process.
Another difficulty with past interlock and lock systems for file cabinets has been the expense involved in creating a locking system that will withstand high forces exerted on the drawers. The Business and Institutional Furniture Manufacturer""s Association (BIFMA) recommends that lock systems for file cabinets be able to withstand 50 pounds of pressure on a drawer. Thus, if a file cabinet does not exceed this standard, thieves can gain access to the contents of a lock drawer by pulling the drawer outwardly with more than fifty pounds of force. Many users of file cabinets, however, desire their locking system to be able to withstand much greater forces than this before failure. Increasing the durability of the locking system often adds undesired expense to the cost of building the system.
A number of prior art interlock systems have used cables or straps as part of the interlocking system. Such systems, however, have suffered from other disadvantages. For example, U.S. Pat. No. 5,199,774 issued to Hedinger et al. discloses an interlock and lock system that uses a cable. The slack in the cable is decreased when a drawer is opened. The amount of slack of the cable is carefully chosen during the installation of the drawer lock so that there is just enough in the system to allow only one drawer to be opened at a time. The interlock on whatever drawer is opened takes up this available slack in the cable, which prevents other drawers from being opened at the same time. A similar system is disclosed in U.S. Pat. No. 5,062,678 issued to Westwinkel. This system uses a strap instead of a cable. Both systems suffer from the fact that excessive amounts of force may be easily transferred to either the cable or the strap. In other words, the cable or the strap itself are what resist the pulling force that a person might exert on a closed drawer when either the lock is activated, or another drawer is opened. The tensile strength of the cable or strap therefore determines how much force must be exerted to overcome the interlock or lock. In fact, in the interlock of Westwinkel, the system appears to be constructed so that the pulling force exerted by a person on a locked drawer will be amplified before being applied to the strap. The strap must therefore have a greater tensile strength than the highest rated pulling force that the lock or interlock system can resist. Increasing the strength of the cables or straps typically tends to increase their cost, which is desirably avoided.
In light of the foregoing, the desirability of an interlock and lock system that overcomes these and other disadvantages can be seen.
Accordingly, the present invention provides an interlock and lock that reduces the aforementioned difficulties, as well as other difficulties. The interlock and lock of the present invention allow relatively low-tensile strength cables or flexible members to be used in systems which provide high resistance to theft and breakdown. The system of the present invention further allows changes to cabinet configurations to be easily implemented with little or no additional work required to integrate the new cabinet configuration into the interlock or lock system. The present invention provides a simple construction for locks and interlocks that can be easily manufactured without excessively restrictive tolerances, and which can be easily installed in cabinets.
According to one aspect of the present invention, an interlock is provided that includes a cable, a slack take-up mechanism, a cam, and a biasing member. The slack take-up mechanism is engageable with the cable and movable between a higher slack position and a lower slack position. The lower slack position causes the cable to exist in a relatively lower slack condition. The higher slack position allows the cable to exist in a relatively higher slack condition. The cam is operatively coupled to the slack take-up mechanism and to the drawer. The cam is adapted to switch the slack take-up mechanism from the higher slack position to the lower slack position when the drawer is moved in the first direction toward the open position. The biasing member is adapted to exert a force against the take-up mechanism that urges the slack take-up mechanism toward the lower slack position. The force of the biasing member may have a magnitude that is independent of the magnitude of the force exerted on the drawer in the first direction.
According to another aspect of the present invention a cabinet is provided. The cabinet includes at least one drawer, a frame, an elongated, flexible member, and an interlock. The interlock is adapted to prevent the drawer from opening when the elongated, flexible member is in the lower slack condition, and to allow the drawer to open when the flexible member is in the higher slack condition. The interlock includes a slack take-up mechanisms that changes the flexible member from the higher slack condition to the lower slack condition when the drawer is opened. The slack take-up mechanism is further adapted to exert a force on the elongated, flexible member that has a magnitude that is independent of a force applied in the first direction to the drawer.
According to still other aspects of the present invention, the interlock may be in communication with a lock that is adapted to selectively alter the condition of the cable. The interlocks may be secured to drawer slides that are removable from the cabinet. A cable guide may be included as part of the interlock to snap-fittingly receive the cable and retain it in engagement with the interlock.
The various aspect of the present invention provides an interlock and lock system that is versatile, resistant to high forces, and easily installed. These and other benefits of the present invention will be apparent to one skilled in the art in light of the following written description when read in conjunction with the accompanying drawings.